WLAN is a wireless local area network communications technology operating at an unauthorized band, and has a very high data transmission rate. LTE is a cellular communications technology operating at an authorized band, and may provide reliable and high-efficiency wireless communications for mobile user equipments. As increase of the number of smart user equipments, the amount of traffic data of the user equipment tends to increase tremendously. Especially in hotspot areas, as the amount of traffic data is giant and demands for traffics (for example denoted by bearers) are complex and varied, challenges are brought to existing LTE systems.
An LTE and WLAN aggregation system is under study in the 3rd Generation Partnership Project (3GPP), in which is expected that wireless resources of a WLAN system operating at an unauthorized band and an LTE system operating at an authorized band may be aggregated, so that the both systems may provide services for user equipments at the same time, and user experiences may be improved.
FIG. 1 is a schematic diagram of an architecture of a protocol stack of an LTE and WLAN aggregation system, in which a case of downlink is shown. As shown in FIG. 1, the aggregation system mainly includes three parts: a base station (such as an eNB) at an LTE network side, an access point (AP) at a WLAN network side, and a user equipment (UE). The eNB mainly carries out an LTE protocol stack, the AP mainly carries out a WLAN protocol stack, and the UE has protocol stacks of LTE and WLAN at the same time.
The LTE protocol stacks at the eNB side and the UE side mainly include the following protocol layers: a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and an LTE media access control (MAC) layer. And the WLAN protocol stacks at the AP side and the UE side mainly include the following protocol layers: a logical link control (LLC) layer, and an IEEE 802.11 MAC layer.
For example, a logical node connecting LTE and WLAN is defined as a WLAN termination (WT) in the 3GPP. And the WT is mainly responsible for interaction of the two protocols and processing of user plane data packets.
The above aggregation system may simultaneously carry multiple traffics (such as bearers) of the same UE. The system establishes an individual PDCP layer entity respectively in the eNB and the UE for each traffic. As shown by the arrow in FIG. 1, data of a PDCP protocol data unit (PDU) of the same traffic may be split into two data streams in the PDCP layer, which are simultaneously transmitted in an LTE link and a WLAN link. And data of multiple traffics which are branched into the WLAN link is carried by a unique LLC layer entity and an MAC layer entity.
The WT is a logical node defined in the 3GPP, and interior of which may be achieved by multiple protocol layers or multiple functional modules. A physical position the WT may be in an AP, or may be independent from an AP. The WT performs processing on a PDCP PDU issued by a PDCP layer, and delivers the processed data to an LLC layer. The WT needs further to accomplish functions of multiplexing and demultiplexing for data of multiple traffics in an LLC entity. And furthermore, the WT should provide some feedback information to the PDCP layer, characterizing a transmission situation of the PDCP PDU in the WLAN link, so that the PDCP layer determines a scheme for data stream division and forwarding and performs traffic controlling.
It should be noted that the above description of the background is merely provided for clear and complete explanation of this disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of this disclosure.